In the known state of the art, ventilating and air-conditioning units, such as are employed for example in buildings, are as a rule outfitted with heat recycling systems, whereby the heat of the spent exhaust air, especially in the Winter, is extracted by way of a heat exchanger system and conveyed if need be onto the outside air to be heated up. Different systems are available to this end. One advantageous system which has been established is the integrated circuit system wherein one heat exchanger is located in the exhaust air, the so-called exhaust air heat exchanger, to extract the heat from the spent exhaust air, and one heat exchanger in the outside air, the so-called outside air heat exchanger, to deliver the heat recovered from the exhaust air. In the present state of the art, these systems essentially serve exclusively for the recycling of heat.
Known as an added function is, for example, the indirect adiabatic evaporative cooling, wherein when there is a need for cold to cool the outside air, the expelled exhaust air is adiabatically cooled in a water evaporator device, and such relative cold is channeled from the exhaust air by way of the integrated circuit onto the warmer outside air.
Similarly, these efficient heat exchanger systems permit other functions, which may be located within the heat exchangers themselves or in the integrated circuit, as for example the integrated after-heating or after-cooling on the wet end, a system for desiccation cooling and desiccation cold recycling, the uptake of circulating cold for free cooling, for refrigerating machine cold recovery as well as the integration of naturally present heat and cold potentials in the circuit for heating and cooling of air.
Another important energy-saving function in ventilation plants is the so-called nighttime cold cooling, that is to say, for example in the Summertime, when the overnight temperature is distinctly below the daytime temperature, channeling directly into the rooms of a building at nighttime the colder outside air through ventilating ducts. In such a nighttime-cold cooling, the installed heat recovery system may remain inactive, that is to say, the heat recovery system may be completely shut off or to say the least, the heat recycling output may be reduced by adjusting the quantity of water circulating in the integrated circuit.